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748 Spark Plug

Discussion in '748 / 916 / 996 / 998' started by Bison, Jul 11, 2019.

  1. Hello again folks.
    Took the plugs out of my 2002 748S slabside, (ST4 type heads) they are RA4HC, now, some sites say RG4HC, but more say RA59GC, confused is the word. Any suggestions?, anyone else have the same bike?, which plugs.
  2. What does the owners manual say?
    • Agree Agree x 1
  3. Unfortunately, I don't have one, Mr Haynes says RA59GC. Just wondered if the spec was different for the ST4 heads on the last 748's, ST4 plug is RA59GC as well though. I'll probably just get those.
  4. 67090121A probably :thinkingface:
  5. These are all the same Ducati part number if that helps:

    Capture1.JPG Capture2.JPG
  6. My manual says Champion A 55 V but I've just noticed yours is an S and mine is an R - but having looked it up and typed this out.......:)
    Good luck with finding the answer
  7. You're R is on the list above...
    • Like Like x 1
  8. That's what web sites say when Googling the Ducati part Number too.
  9. https://www.carlsalter.com/ducati-service-manuals.asp
    • Disagree Disagree x 1
  10. Factory manuals state RA59GC as well as the MY02 748 owners manual. Most avoid Champion plugs and go for NGK, some avoid Iridium but many swear by them (I have sworn at them)

    RG4HC are the ones specified for 998s in the same owners manual Issued for MY02 748/998. If you don't read the manual correctly you might think the RG4HC is the one for the 748
    #11 Denzil the Ducati, Jul 11, 2019
    Last edited: Jul 12, 2019
  11. Thanks Folks, great info, and real quick too. I'll bet that's exactly what's happened, a quick scan of the manual and someone has ordered and fitted 998 plugs by mistake.
    I've ordered the Champion RA59GC.
    Thanks again,
    • Like Like x 3
  12. Having Testabassa heads on the 2002 748 doesn't change the type of plug to earlier 748s. Not sure though that the plugs for the 998 would be the same as that's a Testastretta. Of note, none of the 748R had the dropped cam heads, even the 2002.
    I think it's important make sure the plugs that will fit down the head with enough room for the socket
  13. NGK DCPR9E are more reliable. You can run the Iridium but there’s little in it.
    • Like Like x 1
    • Thanks Thanks x 1
  14. I’ve the same bike and I’m running ngk iridium DCR9EIX
    • Like Like x 1
  15. As listed by NGK on their website for 748S model years 2000 - 2004.
  16. DCR9EIX -- Do you guys alter the gap? Preset to 0.8mm

    Copper Champion plug in the manual is 0.6mm

    Anybody run the racing NGK plug , R2525-10
  17. No, I run them with the preset gap. The ignition system is quite capable of firing the larger gap which helps reduce plug fouling.
    In fact NGK do not recommend altering the gap as the fine centre electrode is easily damaged.
    • Agree Agree x 1
  18. Thanks Derek

    I have the correct tool to gap them without damaging them

    Might try 0.9mm, 0.95
  19. Interesting.
    Like Derek, I always stuck with the preset gap but I have read recommendations to increase the gap for an even fatter spark. It would be interesting to hear how you get on...

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